Guiguzi (鬼谷子) is the Chinese title given to a group of writings thought to have been compiled between the late Warring States period and the end of the Han Dynasty. The work, between 6,000–7,000 Chinese characters, discusses techniques of political lobbying based in Daoist thinking.

There has been much speculation about the identity of the writer of Guiguzi, the origin of his name (literally 'The Sage of Ghost Valley') and the authenticity of the work as a whole. While there has been no final outcome to this discussion, Chinese scholars believe that the compilation reflects a genuine corpus of Warring States period writings on political lobbying. Most writers doubt the assertion that the Guiguzi was written by a single personality, Guigu Xiansheng (鬼谷先生), who was said in the Records of the Grand Historian to have been the teacher of the late Warring States political lobbyists Su Qin and Zhang Yi. A tradition that Guigu Xiansheng was the teacher of renowned Warring States generals Sun Bin and Pang Juan is also considered to be a late confabulation. The association of the name Wang Xu (王詡) is not generally held to be supported. There is no material in the text to support the view held by some that Guiguzi is a book on military tactics.

The contents of the Guiguzi text cover the relationship between lobbying techniques and the theory of yin and yang, techniques of political evaluation of the state, evaluation of political relationships between state leaders and ministers, psychological profiling of lobbying targets and rhetorical devices.

There have been translations of Guiguzi into modern Chinese, German, English, and Russian. Almost all modern annotated texts and western translations rely heavily on the explanations of the texts attributed to the Eastern Jin scholar Tao Hongjing.